Barcelona put on a stunning show at the Camp Nou Tuesday night, mesmerizing the Milan defense with quick passes and darting runs, reminding us all what has made them the most feared team on the planet over the past five seasons. In the end, they fired four passed the Milan rearguard and kept a clean sheet at the other end, becoming the first team in Champions League history to overcome a 2-0 first leg deficit.

And they were well worth their wide margin of victory. JordiRoura shuffled his front line somewhat as David Villa (finally?) took his place at the point of the Barca attack, with Pedro moving out to the left side and Messi sliding back into an attacking midfield role and occasionally drifting into his old right wing position.

The change of tactics certainly had an effect, but the biggest departure from the past several weeks was in Barcelona's general approach, both with possession and in defense. The passing was incisive, forward-looking, and above all, quick, with players all over the pitch making first touch passes in the final third, rather than settling the ball and slowing down the attack. And when they lost the ball, the pressure on the Milan players was fast and furious. With nowhere to go and no one to pass to, Milan were giving the ball away with alarming consistency.

Barcelona's sharpness was on display inside the first five minutes when Pedro played Iniesta's pass back to Busquets with a single touch. With Ambrosini still on his way to pressure to Pedro, Busquets collected the pass from the diminutive winger with plenty of time to pick out a truly clever ball between Montolivo and Shaarawy to the feet of Lionel Messi. Rather than attempt to turn as he might have done in recent weeks, Messi already knew where the ball was headed, as Xavi had maneuvered in between Montolivo and Milan's last line of defense. A quick one-two with Xavi, and Messi was poised for his stunning finish into the top corner.

Iniesta and Xavi each forced fantastic saves from Christian Abbiati, while Pedro had a serious penalty shot waved away after being bungled over by Abate.

Meanwhile, Barca were playing a dangerous game at the other end as they continued to push forward for goals. They were always going to need a bit of luck to keep Milan out for the whole of 90 minutes, and the football gods were there to bestow it on 38 minutes. Mascherano's colossal misjudgment of a simple header let Niang clear through on goal, but with only Valdes to beat, the Frenchman slotted his effort off the woodwork.

Sighs of relief echoed around the Camp Nou as Barcelona resumed their task at Milan's end of the pitch.

Their pressure paid off soon thereafter as Iniesta robbed Ambrosini of possession 35 yards from goal, squeezing between him and Flamini to advance forward into space. With pressure late in arriving, Iniesta delivered another incisive pass, squeezing the ball just past the feet of Montolivo into the path of Messi, who this time did the rest of the work himself.

It was more of the same in the second half when Mascherano—pressuring extremely high up the pitch for a center half—picked off Zapata's pass, pinging the ball into Iniesta near the top of the penalty arc.

Again, two lightning-quick first-time passes, from Iniesta to Xavi, and Xavi to David Villa, and Barca were in.

On this occasion, Constant must take some blame, as he impulsively dived toward Xavi's pass in a vain attempt to pick it off, leaving Villa with an easy path to goal.

But the Spanish marksman proved his worth and validated his choice in the team with a sublime finish to tip the tie in Barcelona's favor.

For about 10 minutes thereafter, Barcelona maintained complete control over the match, penning Milan into their own half and threatening a fourth goal to put the tie away.

But Milan—urged on by the introductions of Sulley Muntari, Robinho, and Bojan Krkic—started to apply pressure of their own.

Their newly attacking posture very nearly paid off when Bojan left Pique for dead on the left side of the attack and swung in a low cross for Robinho, but Jordi Alba was there with a game-saving challenge to deny the Brazilian.

And Alba showed that—despite the doubters—he can be effective at both ends of the pitch, traversing its entire length to get on the end of Alexis Sanchez' curled pass in the 92nd minute to seal the tie.

Alba started his extraordinary run as literally the farthest field player back, less than 25 yards from his own goal line. He literally sprinted past the entire Milan team as they watched and waited for their defenders to regain possession.

As for the idea that Alba and Alves should play more conservatively, I have a better one: Barca, never change.

In the end, Milan may not have been at their shining best on the night, but it was a remarkable performance from Barcelona, as they took control of the match from the first minute and maintained a frightening energy through the hour mark. There's simply no defending goals like the first one; it was just too good. They achieved not only an unlikely comeback, but a redemption—of their style and their approach to the game.

And it was a redeeming night for Messi as well, as he continues to silence any doubts and doubters that remain. He again stepped into the fray and provided the critical goals at the crucial times—and what goals they were.

The quarterfinals are shaping up to be a mouthwatering affair, with several teams left in the competition who could trouble Barcelona. But if their season has hit its low point, who among the teams in Europe could stem the tide of their rise now?